Support Q & A

I have a few questions about the Sequence Diagrams as implemented in Astah.

When either a Synchronous Message or Asynchronous Message is added to a Sequence Diagram, a block of time is shown at both ends of the arrow. According to the SysML specification, it should be possible to show messages with no time block shown (indicating no duration at either end of the message). How do you hide the boxes in Astah? (I think these are called "Execution Specification" in the SysML spec). In Astah, I can't figure out how to remove, hide or reduce them to invisible size.

Second Question: According to the reference material I have seen, the duration constraint should be able to be specified for the Execution Specification time blocks. When I try to insert a duration constraint, I have to select the message arrows, not the Execution Specification time blocks. Is there way to show the duration constraint on the time block and not between arrows? Sometimes there is no arrow at the end of the time block.